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Date: Tue, 25 Apr 2017 11:05:58 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: PaX Team <pageexec@freemail.hu>, LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH] x86/refcount: Implement fast refcount_t handling
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On Mon, Apr 24, 2017 at 03:37:32PM -0700, Kees Cook wrote:
> On Mon, Apr 24, 2017 at 3:01 PM, Peter Zijlstra <peterz@infradead.org> wrote:

> > It does not. It just got free'ed. Nothing will stop the free from
> > happening (or already having happened).
> 
> Well, yes, but that's kind of my point. Detecting inc-from-0 is "too
> late" to offer a protection. It offers notification of a bug, rather
> than stopping an exploit from happening.

Well, your setup (panic_on_warn et al) would have it panic the box. That
will effectively stop the exploit by virtue of stopping everything.

And warn/bug/panic etc.. are I think a better option that silently
letting it happen.